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SubjectRe: new execve/kernel_thread design
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Hi Al,

2012/10/17 Al Viro <viro@zeniv.linux.org.uk>:
> On Wed, Oct 17, 2012 at 05:07:03PM +0100, Al Viro wrote:
>> What happens during boot is this:
>> * init_task (not to be confused with init) is used as current during
>> infrastructure initializations. Once everything needed for scheduler and
>> for working fork is set, we spawn two threads - future init and future
>> kthreadd. The last thing we do with init_task is telling init that kthreadd
>> has been spawned. After that init_task turns itself into an idle thread.
>> * future init waits for kthreadd to be spawned (it would be more
>> natural to fork them in opposite order, but we want init to have PID 1 -
>> too much stuff in userland depends on that). Then it does the rest of
>> initialization, including setting up initramfs contents. And does
>> kernel_execve() on /init. Note that this is a task that had been created
>> by kernel_thread() and is currently in function called from
>> ret_from_kernel_thread(). Its kernel stack has been set up by copy_thread().
>> That's where pt_regs need to be set up; note that they'll be passed to
>> start_thread() before you return to userland. If there are any magic bits
>> in pt_regs needed by return-from-syscall code, set them in kthread case of
>> copy_thread().
>
> PS: I suspect that we end up with the wrong value in childregs->msr;
> start_thread() only add MSR_UMS there. I'd suggest running the kernel
> with these patches + printk childregs->msr the very first time start_thread()
> is called and see what it prints, then working kernel + such printk and
> compare the results...

sorry for taking this so long.
I have looked at it and fix it.

Here is the branch based on rc5 (information below)
and here is giweb.
http://developer.petalogix.com/git/gitweb.cgi?p=linux-2.6-microblaze.git;a=shortlog;h=refs/heads/viro/arch-microblaze-rc5

I have also looked at your sys_fork / sys_vfork / sys_clone unification
and I have fixed it for Microblaze.

Also I have done some tests on it for sure.

I would add sys_execve/kernel_execve/kernel_thread patches to my next branch.
Are you OK with that?

Do you need to test anything else for MB?

Thanks,
Michal


The following changes since commit 77b67063bb6bce6d475e910d3b886a606d0d91f7:
Linus Torvalds (1):
Linux 3.7-rc5

are available in the git repository at:

git://git.monstr.eu/linux-2.6-microblaze.git viro/arch-microblaze-rc5

Al Viro (5):
microblaze: switch to generic kernel_thread()
microblaze: switch to generic kernel_execve()
microblaze: switch to generic sys_execve()
generic sys_fork / sys_vfork / sys_clone
microblaze: switch to generic fork/vfork/clone

Michal Simek (3):
microblaze: Fix bug with schedule_tail
microblaze: Define current_pt_regs
microblaze: Remove BIP from childregs

arch/Kconfig | 11 ++++
arch/microblaze/Kconfig | 3 +
arch/microblaze/include/asm/processor.h | 10 +---
arch/microblaze/include/asm/unistd.h | 6 ++
arch/microblaze/kernel/entry-nommu.S | 20 +++-----
arch/microblaze/kernel/entry.S | 57 ++++-------------------
arch/microblaze/kernel/process.c | 77 ++++++++++---------------------
arch/microblaze/kernel/sys_microblaze.c | 53 ---------------------
arch/microblaze/kernel/syscall_table.S | 6 +--
include/asm-generic/syscalls.h | 7 +--
kernel/fork.c | 43 +++++++++++++++++
11 files changed, 111 insertions(+), 182 deletions(-)


--
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian


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